1. Your mouth is dry and your tongue is swollen

iStockphoto.com

The No. 1 sign that you’re not sufficiently hydrated is probably the most obvious: you’re thirsty. The mouth dries out and your tongue becomes slightly swollen as your body cries out for hydration — signs that should not be ignored. The best way to avoid dehydration is simply to drink water whenever thirsty. If, however, you’re drinking enough water and you’re still noticing signs of dehydration, then some other underlying condition may be source of your problem.